[libtorrent] libtorrent-1.1.3 released

[Arvid Norberg]

https://github.com/arvidn/libtorrent/releases/tag/libtorrent-1_1_3

1.1.3 release, changes since previous release

* removed (broken) support for incoming connections over socks5
* restore announce_entry's timestamp fields to posix time in python binding
* deprecate torrent_added_alert (in favor of add_torrent_alert)
* fix python binding for parse_magnet_uri
* fix minor robustness issue in DHT bootstrap logic
* fix issue where torrent_status::num_seeds could be negative
* document deprecation of dynamic loading/unloading of torrents
* include user-agent in tracker announces in anonymous_mode for private
torrents
* add support for IPv6 peers from udp trackers
* correctly URL encode the IPv6 argument to trackers
* fix default file pool size on windows
* fix bug where settings_pack::file_pool_size setting was not being honored
* add feature to periodically close files (to make windows clear disk cache)
* fix bug in torrent_handle::file_status
* fix issue with peers not updated on metadata from magnet links